Video attachments from RSS feeds can't play in Chromium web browsers (Android)

[Philippe-Choquette]

Steps to reproduce the problem

1. With a Chromium-based web browser on Android (e.g., Chrome, Opera, etc.), access the RSS feed of some Mastodon profile (e.g., https://mstdn.social/@noelreports.rss) who makes posts with videos.
2. Open the video attachment URL of one of the posts (e.g., https://media.mstdn.social/media_attachments/files/112/452/246/742/536/360/original/aa87a9a2d3aa7403.mp4).

Expected behaviour

The video plays as expected

Actual behaviour

The video buffers for a second, after which the "corrupt file" icon appears on the overlay. The video doesn't play.

Detailed description

I am not a user of Mastodon, but I use the RSS feed capability to follow the activity of some profiles related to the Russo-Ukrainian war. I have them set up with the Inoreader app on Android. However, since the app doesn't support the playback of video attachments within the RSS posts, I have to tap the link to open them in my web browser, Opera. However, for some reason, it cannot play the video. The same issue occurs in Chrome, which shares the Chromium engine with Opera. Meanwhile, it plays properly in Firefox, which has its own engine. I can only conclude that the issue is between Mastodon and the Chromium engine on Android.

The videos play correctly if you view the posts on the web GUI of Mastodon. Also, videos of the same format (MP4) do play correctly on other websites. The issue really seems unique to the RSS feed from Mastodon.

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Opera (Android)

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Google Chrome (Android)

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Firefox (Android)

Mastodon instance

mstdn.social

Mastodon version

v4.2.8

Browser name and version

Opera 82.2.4342.79505 / Chrome 124.0.6367.171

Operating system

Android 12

Technical details

No response